This is weird on so many levels. I work with a guy that has been in a relationship with his second cousin for over 15 years and a lot of people have come to accept that but you are talking about the woman that gave birth to you.

Is it possible she is just teasing you? Some people have a very unusual sense of humour and my Wife's Uncle is always telling her how sexy his hairy butt is and how real men do skids but he is just stirring her and it could be your Mum is doing the same thing and thinks you would get grossed out over talking about stuff like that with her because she is your Mum.